Investigation on custom USB issue

[astella]

To the kind attention of Nordic support team,

We have this custom board using nRF52833 powered up from usb and in high voltage mode (ldo). The problem is that we are doing hundreds of usb enumerations after power up that are going ok. Then we can experience these series of 5/6 usb enumerations in a row that are failing (see attached report).

We are trying to understand if it is a sw/hw issue. This report could make think an hw thing as we suddenly get all those CRC errors. Is it possible in your opinion as well? What could be something to definitely look at in your opinion?

In latest nRF52833 product specifications Rsource,vbusvddh is max 3.8 ohm, and I'm not sure about this value has already been measured/tested in laboratory. Could some different value explain such a behavior? You suggest to double check usb lines impedance?

Could this issue have roots in firmware as well according to your opinion and the report shared? For example in our fw we have got enumeration going on after gzll has been activated. And gzll resources are with very high priority, so that could in theory block usb enumeration. But should be the case, we should only get timeout errors when using usb analyzer.  

This is in part a follow up of

https://devzone.nordicsemi.com/f/nordic-q-a/79119/nrf52833-app_usbd_evt_power_ready, just going on with our investigation in custom usb board enumeration. 

Thank you for your amazing work and every suggestion/opinion is very well welcome

Best regards, 

[ovrebekk]

Hi 

A couple of follow up questions first:

1) Have you tested this on more than one board?
If yes, is the issue present on all of them?

2) Have you been able to test this on a standard DK to see if the problem is the same?
This can give an indication of whether or not the issue is hardware related. 

3) Would it be possible for you to run a test with Gazell disabled in order to verify whether or not this could be related to the problem?

4) Has the hardware schematic and/or layout been reviewed by us?

Best regards
Torbjørn

[astella]

Thank you very much ovrebekk for your reply and your suggestions. We will talk internally about your proposal to share schematic/layout, very kind of you. And also your suggestion about building a complete DK prototype is really interesting and we will remember that for the future also.

I'll follow up as soon as I have news from my colleagues.

Best regards

[ovrebekk]

Sounds good. Just let me know when you have got some input on my earlier questions